PROJECT SUMMARY Diabetic Retinopathy (DR), a major complication of diabetes, is the leading cause of blindness in working-aged adults in the United States. DR is characterized by neurodegeneration and microvascular abnormalities. Current therapies for DR treat advanced stages of the disease, particularly the vasculopathy and have adverse side effects. Lack of effective treatments to prevent the incidence or progression of DR is a major problem in the vision field. A critical barrier to the progress in reducing vision loss in diabetic patients is the lack of understanding of the molecular mechanisms that lead to diabetes-induced neuronal damage which could serve therapeutic targets. Our goal is to contribute to the treatment of DR, by defining the specific role of Spermine Oxidase (SMO, an important enzyme in polyamine metabolic pathway), in mediating neuronal damage in the diabetic retina and by demonstrating its potential as a therapeutic target for DR treatment. Our central hypothesis is that diabetes causes upregulation of SMO in retinal neurons, resulting in increased polyamine oxidation and release of acrolein. Our hypothesis predicts that formation of various protein-acrolein adducts causes oxidative damage in diabetic retina, leading to neuronal dysfunction. Our objectives are: 1) determine the impact of SMO overexpression/downregulation in mediating neuronal damage and dysfunction in experimental model of DR; 2) characterize molecular mechanisms involved in SMO-induced neuronal damage in the diabetic retina, and 3) determine the therapeutic potential of inhibiting SMO in DR. Our expected outcomes include 1) demonstration of alterations in inner retinal neuronal survival and function in response to manipulation of SMO expression in DR models; 2) identification of SMO induced molecular changes by which neuronal damage occurs in diabetic retina; and 3) preservation of retinal structure and function in response to SMO inhibition in experimental DR model. Our studies will impact the field of diabetic retinopathy by providing new and significant information on mechanisms by which neurons become dysfunctional in the diabetic retina and thus can lead to the development of accurate and efficacious targeted therapies to delay or prevent vision loss in DR patients. The concept of limiting neuronal injury is also applicable to other vision disorders such as glaucoma and optic neuropathy. Modulating SMO function to reduce oxidative modifications of proteins and mitochondrial dysfunction in the retina can facilitate towards clinical practice by providing new therapies for vision loss worldwide. Aim 1 will test the hypothesis that upregulation of SMO causes neuronal injury in the diabetic retina. Aim 2 will test the hypothesis that upregulation of SMO causes increased polyamine oxidation, acrolein- protein adducts formation, and mitochondrial dysfunction in the diabetic retina. Aim 3 will test the hypothesis that SMO blockade can preserve retinal structure and function in DR.